Changing to Grey
by itstoppedoctober1st
Summary: S4 AU Post-Limey. What if Kate's feelings get the better of her after Castle's attempts to move on without her? Prompt fill from Tumblr.
1. Chapter 1

Disclaimer: Castle is in no way mine. Not even a little bit. The lyrics aren't mine either.

A/N: So this is my first Castle fic. And my first attempt at any sort of fic in years. But I figure in honor of #CastleFanficMonday I would give writing a shot again. From a prompt I found on Tumblr, though I have deviated from it a little. AU Post-The Limey. The lyrics are taken from "This Way" by Michelle Branch. Prompt found at the end.

My eternal gratitude to Maribea for the beta and general hand holding to get this done! You are the greatest! And to Alex for helping to convince me to post.

* * *

 **Changing to Grey**

 _I don't know how long you've been holding on_

 _I don't know how long everything's been my fault_

 _It's getting easier to take the blame_

 _It's getting easier to try and change_

 _She's fun and uncomplicated. That's what he needs right now. Fun and uncomplicated. Not you._ The words echo through her head over and over again as she trudges down the hallway to her apartment. She had thought that getting drinks with Hunt would help her forget for a minute that Castle was moving on and leaving her behind again. She had been so, so wrong. Sitting there with the other man had only made those feelings worse. Even though she knows he was headed to see Jacinda after leaving the precinct earlier, she still felt like she was betraying him by sitting with Hunt. After quickly draining her whiskey sour, she threw a few bills on the table, made a half hearted excuse to the foreign agent and was out the door into a cab before Hunt even had a chance to respond.

 _Fun and uncomplicated. Fun and uncomplicated._ She unlocks her front door, throws her keys on the table and collapses onto her couch, finally starting to let all of the emotions of the day sink in. How could he just move on so quickly? When did he become that guy who runs off to Vegas and brings back flight attendants? What happened to the man who had tearfully confessed his love to her as everything faded to black? _Why doesn't he care anymore?_ She lets these thoughts overwhelm her as she drags herself into her bedroom, wanting nothing more than to crawl into bed and let the tears she had been holding back all day finally fall.

The next afternoon, Kate slowly lifts her head and rubs at her eyes to clear her vision, hours of tears and restless sleep still making her groggy. As she tries to figure out what had jolted her back into alertness, she hears it again, a pounding on her front door. She slowly drags herself out from under the blankets and looks in the mirror. Her disheveled hair and red, puffy eyes make her look almost as sick as she had tried to make herself sound when she called in sick to the precinct that morning. "Great," she mumbles to herself as she grabs her robe, wraps it around herself, and heads for the living room. "At least I look the part."

Looking through the peephole, she is unsurprised to see her best friend on the other side. She reluctantly opens the door as Lanie brushes by her quickly. She heads straight for the kitchen and opens a drawer to pull out a corkscrew for the bottle of wine in her hand before she finally addresses Kate, "All right honey, what's going on? And don't give me any of this 'I'm sick' bullshit because I'm not buying it!" She grabs two glasses from the cabinet while Kate closes the door and heads for the couch, accepting that Lanie won't be satisfied with any stories other than the truth.

"How did you even know I was home, Lanie?" At her friend's answering glare, she knows. "Espo. Of course he texted you. I didn't think you guys were even talking right now."

"Don't change the subject here Kate," Lanie admonishes, "Javi and I are talking just fine when the subject is you and a certain writer boy who's been suspiciously MIA from the precinct recently." She walks into the living room with two glasses of wine, stopping to place Kate's on the coffee table in front of her before settling herself in a chair and focusing her attention back on Kate. "So what's going on?"

"I can't do this anymore, Lanie," Kate sniffles and wipes at her eyes as she reaches for her glass of wine. "I can't watch him walk away again, especially not with someone else. Not after everything we've been through. Not after we were so close. I thought we were on the same page, I thought he was ok with waiting until I was ready. I guess he got tired of waiting, I just don't know why."

"Oh, honey, I know," Lanie tries to console her. "I saw him with that blonde bimbo at that scene the other day, acting all of the Page Six playboy he pretended to be four years ago." She changes tactics, seeing how uncomfortable her friend is becoming at her mention of Castle's behavior at the crime scene. "You know what you need? You need to get away for a little while. Take a week to sort your thoughts out and figure out what you really want to do. Use some of those vacation days that are piling up again. And go somewhere else besides that cabin, that place will just make you lonely all over again."

Kate sighs into her pinot noir and takes a long gulp. "I guess you're right, I do need a break. My Aunt Theresa has a house up on the Cape, maybe I will take her up on her offer to use it."

"That sounds like a great idea. Clear your head and get your focus back, then come back so you can talk to him." Lanie gets up from her seat and moves to sit on the couch next to Kate, setting her wine glass down on the counter next to hers. "Now let's find the most ridiculous, non-romantic movie there is and forget about the writer of yours for a little bit."

The next morning, after another night of tossing and turning with very little sleep in between, Kate rolls out of bed with her alarm and pads into the bathroom, intending to shower and dress quickly before heading for the precinct. After Lanie had forced some food into her the night before and then headed home, she had tried to go back to bed and get some real rest, but sleep had once again eluded her. Her mind had instead chosen to replay her interactions with Castle the last few weeks over and over in her head, trying to figure out where she had gone wrong. It didn't help that the man himself had texted her around midnight, informing her that he was planning to take a few days to write at home since there were no active cases. However, with his planned absence, she knew it would be the perfect opportunity to slip in and out of the precinct long enough to talk to Gates and then leave the city with minimal excuses.

After a brief scalding hot shower, she steps out and wraps a towel around herself before moving to wipe down her steaming mirror and look at her reflection. Noting the dark circles under her eyes from three nights of minimal rest, she reaches into her makeup basket for some concealer and gets to work at making herself look presentable for the upcoming conversation with her captain.

An hour later, the elevator doors open and Kate takes in the bustle of the homicide floor as she steps out. After nodding in greeting to Ryan and Esposito, she heads straight to the break room for some caffeinated liquid courage before her talk with Captain Gates. Even after all these years she still can't figure out how to work the professional grade machine that Castle had gifted to the unit, so she opts instead for a cup of plain black coffee. After downing it quickly and burning her tongue in the process, she slips out and knocks on the Captain's door.

Gates looks up and nods at her lead detective. "Detective Beckett, what can I do for you?"

"Sir, are you available for a few minutes? I'd like to discuss something with you." Kate folds her hands together and looks at the ground, much more timid than her usual interactions with her superior.

"I think I have a few minutes to spare before my next conference call, Detective, take a seat." Gates gestures to the chair on the other side of her desk. Kate does so reluctantly, still staring at her hands before she speaks again.

"I'd like to take some time off. Starting today if that's possible. I know I don't have much paid leave left after last summer, but I'd like to use it anyway. I just … I'm having trouble focusing. And I'm not sure if my heart is in this job anymore. I'd like to step away for a while and figure that out."

Gates takes in the woman sitting before her, noting the exhaustion and sadness in her eyes. She feels a pang of sympathy for her subordinate as she reaches for a calendar behind her. "Well, Beckett, you don't have any open investigations currently, so I suppose Ryan and Esposito can pick up the bulk of your workload until you return. How much time do you think you will require?"

Kate glances up, looking Gates in the eye for the first time since her initial knock, and brushes a stray lock of hair behind her ear. "That's the thing," she hesitates. "I'm not really sure how long I'm going to be gone. A few weeks at least? Until I figure out what I'm going to do."

Gates peers at her over her glasses, considering her request carefully before speaking. "Well, I can grant you two weeks of paid personal leave to start, and why don't you get in touch with me toward the end of that time to discuss your return date. I will warn you though, Detective, that any additional time beyond those two weeks will have to be unpaid leave."

Kate breathes a sigh of relief. "I understand, Sir, and that sounds more than fair. Thank you, Captain." She pauses before continuing. "I have one more favor to ask. Could you wait until I leave to inform Detectives Ryan and Esposito? I'm not prepared to explain all of this to them just yet."

"I suppose that would be all right. We'll talk in ten days or so then. You're dismissed." Kate slowly rises from her chair and turns to leave the office before she is stopped by her Captain's voice once again. "Oh, and Beckett? I do hope to see you back here sooner than later. You are a great asset to this city … and to me."

Kate looks back with the beginning glimmer of a smile. "Thank you, Sir. I appreciate that." She turns and walks quickly out of the office. She spots the boys, distracted by something on Ryan's computer screen, and darts back toward the elevator quickly before her presence catches their attention. Luckily, the elevator arrives quickly, and she is behind the doors and on her way back to her apartment to pack before they even realize she is leaving.

 _I don't know how long I can justify_

 _I'm tired of making up reasons you're not on my side_

 _And I would never talk to her that way_

 _No I would never talk to her that way_

Castle strides onto the homicide floor of the Twelfth carrying two cups of coffee. After four days off, the place feels a little foreign to him, and he is surprised not to see Beckett in the bullpen already. He had texted her last night to let her know he was planning to come back to the precinct that morning, but it had been late and when he didn't receive a response, he figured she had just gone to sleep already.

The few days off had done him some good. He has been feeling re-energized and ready to get back to a professional relationship with Beckett again. He had worked through his anger and feeling of betrayal with a combination of scotch a few frivolous meals with Jacinda before she headed back to work. He'd also managed to write out a Nikki Heat chapter that had become so emotionally charged as to ensure its destiny was to remain hidden on his laptop forever. However, he had also had plenty of time to think, and had come to the decision that maybe it was time to step away from shadowing at the Twelfth to a more intermittent basis. His return today was for two reasons: to see if the team had caught any interesting cases during his absence, and to explain his intentions to Beckett and the boys.

Glancing around and realizing neither Ryan nor Esposito were present in the bullpen, he places his coffees next to his chair at Beckett's desk and heads for the break room, figuring that his team is chatting or grabbing some morning caffeine. Walking through the door, he finds both of the boys sitting at a table drinking from precinct mugs, but no Beckett.

He wanders over and pulls up a chair next to them. "Hey guys, where's Beckett this morning? Not here yet?"

Both men look up at him in surprise. "H-Hey Castle," Ryan responds. "You mean she didn't tell you? She didn't tell us either, Gates did, but you two are, well you two and you're different so I figured she would have at least-"

Esposito breaks in at this point. "She's not here bro. She's on some kind of personal leave according to Gates, but whatever's going on must be a doozy because she's not answering any of our calls or messages. Lanie knows what's up and that she's ok, but that's all that she'll tell me."

Castle's face drops at this news. Despite his resolve to work on a more professional relationship with Beckett, he's still disappointed that she didn't tell him about her plans to take a last minute leave. He lifts his head to question the boys more when a sharp voice interrupts him before he can even speak. "Detective Ryan! Detective Esposito! A body just popped up, I strongly suggest you get back to work!" As the Captain glares at the group from the doorway, the two detectives jump up and head for the bullpen.

She then turns to the writer, "Ahhhh, Mr. Castle, I see you've returned. Not for long, however, as I'm sure you've been filled in on Detective Beckett's absence. Her leave essentially puts you on leave as well, so I suggest you get out of my precinct before I decide to find a reason to detain you here. That's not a suggestion." At these words, she turns sharply and heads back to the office. A bewildered Castle shuffles out of the break room and through the bullpen to the elevator once again, completely forgetting about the two rapidly cooling cups of coffee on Beckett's desk and pausing only briefly to bid farewell to the boys. Instead of pushing the button for the lobby, however, he heads toward the morgue, hoping to catch Lanie for an explanation.

As luck would have it, he emerges from the elevator to find Lanie walking toward him. She immediately shakes her head. "Uh-uh, not now writer boy, no time for you today, I've got a body calling my name."

She passes by him and he quickly turns to follow, "Where is she Lanie? What's going on?"

"You're an idiot, that's what's going on. You parade around in your Ferrari with some blonde for all the world to see and you're surprised that Kate didn't just go right along with that?" She pauses long enough to turn and glare at him, then continues on as he once again scrambles to catch up.

"It's not like that, Lanie, you know Beckett doesn't care about me like that-"

Lanie swivels around at this and starts on him again. "For someone who doesn't care about you like that, her eyes sure looked like a lot of tears had fallen when I saw her. You have no idea how your actions affected her, do you?" She points a finger at his chest, "Look, you two really need to talk, but right now she is getting some much needed space away from you. She's going to leave the city for a while, stay at a place of her aunt's. I don't know if she's left yet or not, but I'm only telling you this because Beckett's my girl, and you really hurt her so when she comes back, you better be ready to fix it! Now I've got to go, and that's all you're getting out of me." Lanie sweeps away leaving a stunned Castle behind.

Castle bounds up the stairs to Beckett's apartment, hoping to catch her before she leaves for wherever she is going. He makes it down the hall and to her front door and starts pounding, "Beckett? Beckett, can we talk?"

"She's not here," a voice interrupts him from behind. He turns to see Kate's next door neighbor, Mrs. Shanahan, an elderly widow whom Kate helped with her grocery shopping sometimes. "She left on her little trip yesterday, stopped to say goodbye on her way out and to ask me to stop in and water her plants while she's gone."

"Where did she go? When is she coming back?" He pleads, desperate for information.

"I don't know, dear," the older woman replies. "She didn't mention where she was going, but said maybe it'd be a few weeks, maybe more. I'm sorry. I'm sure she'll give you a call once she gets settled." She turns and goes back into her apartment as Castle's heart sinks.

His knees buckle under him and he sinks to the floor. He's not so sure she has any intent to contact him at all. Just like last summer, he's too late.

Beckett is gone.

* * *

Prompt - Sometime after 4x20/4x21: Heartbroken and barely functioning caused by Castle's recent change of attitude, Beckett files for an indefinite leave of absence without anyone knowing except Gates. Castle finds about this and tries to confront her but she's already gone.

Please review and let me know your thoughts!


	2. Chapter 2

**Disclaimer: Still not mine.**

 **A/N: To say that I've been completely overwhelmed by the response to this story is absolutely an understatement. Thank you so much to everyone for their reviews, follows, and favorites. I appreciate all of you. And especially to those who asked me to continue, you all inspired me to plot out a few more parts.**

* * *

Kate's eyes slowly blink open, squinting against the bright sun of the early morning. She lifts her arm over her forehead and looks toward the window at the evidence of the new sunny day streaming in. _Whoops_ , she thinks. _Forgot to close the blinds again last night. At this rate, I'll never get any sleep._

She slowly rolls out of bed and trudges toward the kitchen, making her way to the pantry in search of something, anything with caffeine. "Three days," she thinks to herself, not realizing she is speaking aloud. "Three days since I've had a real meal and not just snacks to curb the nonexistent hunger. More than three days since I've had any coffee. I really need to actually get some groceries today."

Looking again for something she knows isn't there, she settles for the same thing that has satiated her the last three mornings: a granola bar from the box she had grabbed during her gas and bathroom stop on the way up to the house and some lukewarm tap water to wash it down.

Tossing the wrapper and placing her plastic cup in the sink, Kate makes her way back to the bedroom she has claimed as her own and picks up her phone. No different from last night the notifications stare back at her, the voice mail from her dad and nine texts from the boys and Lanie that she can't bring herself to open.

She has spent her first few days at the beach house the same way she spent those before she left: mostly in bed, splitting her time between sobbing, sleeping and overthinking every interaction she and Castle have had in the last few months in her quest to figure out where everything went so wrong.

 _Today_ , she resolves. _Today is the day I start moving forward. Moving on. If Castle wants to go back to being that guy on Page Six all the time, I can just go back to focusing on work. Just like it was._ Kate can feel her brief moment of confidence slipping away even as her thoughts betray her.

She heads into the bathroom to splash some water on her face and to once again stare at the dark circles that seem to have become a permanent fixture under her eyes. As she heads back into the bedroom, she hears her phone begin to vibrate, the caller id indicating that her best friend is once again trying to reach her. Steeling herself, she accepts the call. "Hey Lanie."

"Girl, how is the beach? Got a good tan going on yet?"

Kate almost smiles at her friend's attempts to make her trip sound like an actual vacation rather than an emotional escape. "Lanie, it's spring in New England, not the Caribbean. It's barely warm enough for me to go on the beach without a jacket. Besides, I haven't really gotten out much yet." She can almost hear the ME rolling her eyes through the phone.

"I know, you're still moping about writer boy. Have you thought about what you might say to him yet?"

"That's all I've thought about. It's just best if he's got his space right now. Plenty of time for him to put himself out there to be Page Six fodder again." Kate justifies her hurtful sarcasm more to herself than to her friend.

Lanie tries to reason with her friend. "Look, I saw Castle yesterday. He's not doing so well either. And Javi told me that Gates kicked him out of the precinct again now that you're gone, so the poor guy really has nothing to distract him."

"He's got Jacinda," Kate responds bitterly. "He's looking for fun right now anyway, she'll be able to provide that for him just fine."

Lanie sighs audibly. "There were no signs he was thinking about anyone else but you when he cornered me in the morgue. I still think the two of you might need some physical space, but Kate? Maybe you should give him a call, at least let him know you're okay. And maybe when you're planning to come back?"

Kate's chest clenches at the thought. "I want to, I really do. He's the only one I really want to talk to right now. But he hurt me so badly, Lanie, more than any other man has ever hurt me and we weren't even anything but friends! I'm just not ready to put myself through that again."

"Girl, first of all, whether the two of you were ready to admit it or not, there sure as hell was a relationship between the two of you. But you are both terrible at communicating and you both managed to screw everything up." Her tone softens at Kate's silence. "Kate, you didn't see his face like I did. He was devastated when he realized you were gone. No matter what stupid ass decisions that boy has made in the last few weeks, there is no doubt in my mind that he loves you. Just talk to him."

"I'll … think about it. That's all I can promise you right now." Kate changes the subject quickly. "I've gotta go, Lanie. Uhhhhh, thanks for calling. I'll talk to you soon. Bye." She hangs up the phone quickly before her friend can protest and throws it beside her on the couch before standing and collapsing into another chair across the room and resuming her earlier stare at her phone.

 _Even by phone, I'm still running. I know what I need to do, I just need to suck it up and do it._ How is it so easy to admit to herself? She squares her shoulders as she takes a deep breath and walks back over to her phone. Summoning her courage, Kate unlocks her screen and sends a quick email before her senses get the better of her.

* * *

Castle's phone lights up and begins to vibrate, startling the writer out of his reverie. He looks down at the screen and notes an incoming call from Lanie. _What could she possibly want?_ he thinks. _Just calling to yell at me again, I'm sure._

Against his better judgment, he swipes to accept the call with a tentative "Hello?"

"Hey Castle," Lanie actually sounds apologetic. "I think I may have been a little too hard on you yesterday. I was looking out for my girl and didn't stop to think about your side of this whole business."

He sighs at her words, his mind focused on the woman who warranted Lanie's anger and apology. He's almost afraid to ask as the words tumble out. "How … how is she?"

"I think that's a question she should answer for herself. But what happened? What changed all of a sudden between you two?"

"She lied to me, Lanie," Castle feels the tears welling up in his eyes again. "She remembers the shooting."

His voices raises as his anger gets the better of him, "A whole YEAR she's known that I love her and she LIED to me. I just … I don't know how to get past that. Why would she lie if she felt the same way?"

"You know that I rarely have the slightest idea what's going through her head. But I will tell you this, Castle. That girl loves you so much that it scares her, and you and I both know there's nothing she's better at than running away from her feelings. Just please promise me you won't give up on her yet."

"I'll try Lanie. I just wish she would talk to me."

"I know, but our girl is stubborn. She won't budge until she's ready. I think we're going to have to give her a little push."

"What does that mean?" A long pause on the other end of the line makes him wonder if the call dropped. "Lanie?"

For the first time since he had met the ME, Lanie's voice sounds tentative. "It means that Kate is going to shoot me when she gets back. Hey writer boy?"

"Yes?" Castle responds, confused.

"I probably shouldn't be doing this, but it's for her own good. She's on the Cape. Not sure where exactly, but her aunt has a place up there." The ME braces herself for the expected onslaught.

"What? The Cape? But why …"

Lanie cuts him off before he can finish. "Because like it or not, you two need to talk. And clearly she's not gonna be the one to start that conversation. I'm sure you can get the address from her dad, just …" She pauses again. "Promise me you'll bring her home. Preferably in one piece."

Castle stands and starts pacing around his office. "Lanie, I've …"

"I know. Go get her." He hears the tone indicating the call has ended, grabs his keys and wallet and runs for the door, his phone dialing a familiar number on the way.

* * *

Kate stares at the clock on the side wall, watching the second hand tick, tick, tick around in a circle, feeling more and more anxious as time passes. Finally, the clock hit 4:00, and she shifts her focus to her phone. A minute or so later and it finally buzzes, the screen indicating the caller she has been waiting for.

"Hello, Dr. Burke," Kate picks up the phone almost eagerly and presses the button to put the therapist on speaker. "Thank you so much for rearranging your schedule to talk to me today."

"Of course, Kate," the therapist responds. "What's going on? Why a phone session?"

"Well, I'm not exactly in the city right now, but this week has been a mess and I should have called earlier."

"What's going on?" Dr. Burke responds calmly to the growing panic in Kate's voice.

"I just don't know what to do anymore. Castle and I have made so much progress this year and I thought he understood and was waiting and now he's just … gone." Her voice cracks as she tries to hold back the tears threatening to spill over again. "And I don't know what I did or what changed his mind but I turned around one day and there he was. With Jacinda. Because she's fun and uncomplicated and everything that I'm not."

"Slow down, Kate," Dr. Burke tries to rein in her rising anxiety. "Start from the beginning."

"That's the problem, I don't even know where to begin. I don't know where it all changed. One day he was there, he was bringing me my coffee and giving me his crazy case theories and then it all changed. After the Boylan Park bombing case, he ran off to Vegas and came back with this … woman. And he's been different ever since. Driving around with her in his Ferrari, blowing off cases to go be with her. He told me that he likes her because she is fun and uncomplicated. Basically the opposite of me." Her tears finally spill over. "He finally realized what a waste it is to wait for me and he moved on."

"Change like that doesn't happen in a day, Kate." Dr. Burke tries to calm his client. "Something must have happened. Now what made you leave the city instead of trying to find out why?"

Kate sniffles as she looks for a tissue around her. Finding none, she wipes her eyes with the back of her hand. "I just couldn't be there anymore. I couldn't see him walk away from me everyday and find happiness with someone else. Not after I was finally starting to be ready to be with him."

"Well, it sounds to me like your communication problems are continuing to stand in your way. If you really want to find a future with Mr. Castle, you need to talk to him. Find out why he is pulling away now."

Kate sighs. "My friend Lanie just keeps telling me the same thing, that I need to talk to Castle. And in my head, I know that's true, but I just can't seem to make myself pick up the phone. I just keep seeing him with her over and over in my head. Walking away. Leaving me behind. And I don't understand why."

"What's clear to me, Kate, is that even though you don't want to hear it, your friend is correct. The only person who can help you understand in this case is Mr. Castle. Maybe you are correct, maybe he is ready to move on with someone else. But just maybe, once again, miscommunication has come between you two. It may be fixable, it may not. But you will never know until you actually talk to him."

"You're right, of course you're right," Kate concedes. "I'll give him a call tomorrow, see if we can set a time to talk once I get back to the city."

"In that case, I think we should wrap things up here today. I had to squeeze you in between patients and it's time I got back on schedule. Why don't you give my secretary a call when you get back and set up a time to come in and see me again."

"Okay, I'll do that. And thanks again, Dr. Burke, I really appreciate you fitting me in. I'll speak with you soon." Kate hits the screen to end the call, her resolve strengthened.

For the first time in three days, Kate actually feels hungry. Knowing there is still very little food in the kitchen, she pulls up the phone number for a nearby pizza place and gives them her delivery order.

As she waits for her pizza to arrive, she thinks about her conversation with Dr. Burke. While she still doesn't know what exactly she is going to say to Castle when they talk, she determines that they must talk. _It's the only way I really will be able to move on._

* * *

A few hours later, as Kate is making sure the house is closed up for the night, she hears a tentative knock coming from the front door. Curious, she turns on the porch light and peeks out the small window in the door, but the glare leaves her unable to tell who is standing there. She very slowly opens the door, and her jaw drops at the figure standing before her.

"Castle?!"

* * *

 **This one is for Maribea. I am so grateful for the beta, the guidance, and the friendship. None of this would have ever seen the light of day without you.**

 **Please review. I'd love to hear your thoughts!**


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